Abstract: A hydraulic motor comprising a cylinder, a stepped piston reciprocatable in said cylinder and having relatively proportioned leading and trailing surfaces, the surfaces together with axially directed surfaces defining, with the cylinder walls, first, second and intermediate cylinder zones, which intermediate cylinder zone is sealed with respect the first zone, valve controlled inlet and outlet of said cylinder in communication with said first zone, a water inlet of said cylinder in communication with the intermediate zone, piston wall portions defining a cylindrical recess opening out into the second zone and passages serving to effect communication between the recess and the second and intermediate zones, a tubular spool valve rod, apertured adjacent one end thereof and formed adjacent an opposite end thereof with a pair of axially spaced apart flanges fitting slidingly into the cylindrical recess, the rod having formed thereon an outwardly directed abutment located intermediate the flanges and the one end o